Articles such as hard disks, semiconductor wafers, delicate optics, MEMS (micro electro-mechanical systems), flat panel displays, masks, reticles etc., often must be precisely cleaned in order to remove contaminants, either during or after a process for manufacturing the articles. For example, resist strip and residue clean typically are needed between etch, implant and deposition steps in IC fabrication processes. Conventional dry-type strip/clean sequences typically use plasma to ash resist and wet chemicals to clean residues. Resist stripping is typically carried out using dry plasma ashing. Conventional O2 plasma ashing at high temperature tends to leave polymeric residues that require acids and/or organic solvents for removal. Wet chemistries generally are not desirable due to non-uniformities, selectivity to exposed layers and incomplete resist removal because of mass transport and surface tension associated with the solutions. A variety of alternative cleaning methods have been employed with varying degrees of success. Certain of such methods that have been attempted involve imparting carbon dioxide snow onto the article to be cleaned. An example of such a conventional carbon dioxide cleaning system is described in U.S. Pat. No. 5,766,061.
Conventional systems generally require multiple tools and multiple processes in which articles to be processed have to be moved from one piece of equipment in order to carry out the desired processing. In addition, the processes used in conventional systems generally combine wet and dry processes, which may be batch or single article systems. For example, in a typical post-etch wafer strip/clean, a semiconductor wafer will go through an asher to remove the bulk of photoresist and once a batch of 25 or so wafers are processed through the asher they are thereafter placed in a cassette and placed in a wet bench. The wafers are processed in the wet bench typically by being moved into multiple chemical sinks to clean the residues, then through a sink of DI water to remove the solvent and finally they are moved to a dryer module to dry the wafers. Such conventional systems have many shortcomings. For example, there tends to be a high capital cost due to the multiple pieces of equipment that are required. There also tends to be a high cost per wafer for the cleaning process due to the price of chemicals and chemical disposal, which often involves the use of hazardous chemicals. There also is lowered throughput due to the wafer transport time from one piece of equipment to the next. Also, wet processes tend to affect material properties such as via corrosion of metal, particularly with copper, and changes in dielectric constant value, particularly with low-k dielectric materials. In addition, in conventional methods semiconductor wafers typically leave the vacuum environment after photoresist stripping and prior to wet cleaning. The exposure to atmospheric air often causes an oxide layer to form, which increases the level of difficulty of cleaning.